[Role of chemotherapy in the treatment of brain tumors].

Chemotherapy is a treatment of choice for children with brain tumors, since 20% are unresectable (hypothalamic and brainstem), or incompletely removed, and since radiation therapy often induces cognitive and endocrine sequellae. However, tumor cell heterogeneity and blood-brain barrier which play a role in restricting delivery of chemotherapy represent limiting factors to its efficiency. Neuroradiological procedures such as CT scan and magnetic resonance imaging may bring objective criteria in order to evaluate the efficacity of chemotherapy. Chemotherapy is tested in phase II trials to identify the most efficient drugs for each histological tumor type. This provides a rationale to elaborate phase III trials where polychemotherapy is combined to surgery and radiotherapy. Attempts to enhance drug penetration, such a high-dose chemotherapy and blood-brain barrier disruption, are under study. Primary and acquired drug resistance are being studied as well as the means of overcoming them.